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              <h2 id="学习笔记-JDK-8新特性之方法引用"><a href="#学习笔记-JDK-8新特性之方法引用" class="headerlink" title="学习笔记 : JDK 8新特性之方法引用"></a>学习笔记 : JDK 8新特性之方法引用</h2><h3 id="简介"><a href="#简介" class="headerlink" title="简介"></a>简介</h3><p><em>当要传递给Lambda体的操作已经有实现的方法时,就可以使用<code>方法引用</code>咯~ 方法引用可以看做是Lambda表达式深层的表达,换句话说 : 方法引用就是Lambda表达式,既函数式接口的一个实例,通过方法的名字来指定一个方法,可以认为是Lambda表达式的一个语法糖~</em></p>
<h4 id="要求"><a href="#要求" class="headerlink" title="要求"></a>要求</h4><p><em>实现接口的抽象方法的参数列表和返回值类型,必须与方法引用的方法的参数列表和返回值类型保持一致</em></p>
<h4 id="格式"><a href="#格式" class="headerlink" title="格式"></a>格式</h4><p><em>使用操作符 <code>::</code> 将类(或对象)与方法名分隔开来</em></p>
<h4 id="语法"><a href="#语法" class="headerlink" title="语法"></a>语法</h4><ul>
<li>对象 :: 实例方法名</li>
<li>类 :: 静态方法名</li>
<li>类 :: 实例方法名</li>
</ul>
<h3 id="基本使用"><a href="#基本使用" class="headerlink" title="基本使用"></a>基本使用</h3><p><em>下面通过一个简单的程序示例,来对比Lambda表达式与方法引用写法之间的区别 :</em></p>
<div class="hljs"><pre><code class="hljs java"><span class="hljs-keyword">package</span> pers.huangyuhui.method;

<span class="hljs-keyword">import</span> org.junit.Ignore;
<span class="hljs-keyword">import</span> org.junit.Test;

<span class="hljs-comment">//定义一个函数式接口</span>
<span class="hljs-meta">@FunctionalInterface</span>
<span class="hljs-class"><span class="hljs-keyword">interface</span> <span class="hljs-title">Printable</span> </span>&#123;
    <span class="hljs-function"><span class="hljs-keyword">void</span> <span class="hljs-title">print</span><span class="hljs-params">(String s)</span></span>;
&#125;

<span class="hljs-comment">/**
 * <span class="hljs-doctag">@project</span>: jdk-learnig
 * <span class="hljs-doctag">@description</span>: Java 8新特性之方法引用的基本使用
 * <span class="hljs-doctag">@author</span>: 黄宇辉
 * <span class="hljs-doctag">@date</span>: 8/18/2019-2:15 PM
 * <span class="hljs-doctag">@version</span>: 1.0
 * <span class="hljs-doctag">@website</span>: https://yubuntu0109.github.io/
 */</span>
<span class="hljs-keyword">public</span> <span class="hljs-class"><span class="hljs-keyword">class</span> <span class="hljs-title">methodTest</span> </span>&#123;

    <span class="hljs-comment">//定义打印字符的方法</span>
    <span class="hljs-function"><span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title">printResult</span><span class="hljs-params">(String s, Printable printable)</span> </span>&#123;
        printable.print(s);
    &#125;

    <span class="hljs-comment">//传统写法</span>
    <span class="hljs-meta">@Test</span>
    <span class="hljs-function"><span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title">testPrintString</span><span class="hljs-params">()</span> </span>&#123;
        printResult(<span class="hljs-string">"hello lambda"</span>, <span class="hljs-keyword">new</span> Printable() &#123;
            <span class="hljs-meta">@Override</span>
            <span class="hljs-function"><span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title">print</span><span class="hljs-params">(String s)</span> </span>&#123;
                System.out.println(s);
            &#125;
        &#125;);
    &#125;

    <span class="hljs-comment">//Lambda表达式写法</span>
    <span class="hljs-meta">@Test</span>
    <span class="hljs-function"><span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title">testPrintStringWithLambda</span><span class="hljs-params">()</span> </span>&#123;
        printResult(<span class="hljs-string">"hello lambda"</span>, s1 -&gt; System.out.println(s1));
    &#125;

    <span class="hljs-comment">//方法引用写法</span>
    <span class="hljs-meta">@Test</span>
    <span class="hljs-function"><span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title">testPrintStringWithMethodRef</span><span class="hljs-params">()</span> </span>&#123;
        <span class="hljs-comment">//对象 :: 实例方法名</span>
        printResult(<span class="hljs-string">"hello lambda"</span>, System.out::println);
    &#125;
&#125;</code></pre></div>

<h4 id="语义分析"><a href="#语义分析" class="headerlink" title="语义分析"></a>语义分析</h4><p><em>例如上例中,<code>System.out</code>对象中有一个重载的<code>println(String)</code>方法恰好就是我们所需要的,那么对于<code>printResult</code>方法的函数式接口参数,对比以下两种写法,完全等效 :</em></p>
<ul>
<li>Lambda表达式写法 : <code>s -&gt; System.out.println(s)</code></li>
<li>方法引用写法 : <code>System.out::println</code></li>
</ul>
<p><em>第一种语义是指 : 拿到参数之后,继而传递给<code>System.out.println</code>方法去处理</em><br><em>第二种语义是指 : 直接让<code>System.out</code>中的<code>println</code>方法取代Lambda. 这种写法复用了已有方案,更加简洁</em></p>
<h3 id="常用的几种方法引用"><a href="#常用的几种方法引用" class="headerlink" title="常用的几种方法引用"></a>常用的几种方法引用</h3><h4 id="通过对象名引用成员方法"><a href="#通过对象名引用成员方法" class="headerlink" title="通过对象名引用成员方法"></a>通过对象名引用成员方法</h4><div class="hljs"><pre><code class="hljs java"><span class="hljs-keyword">package</span> pers.huangyuhui.method;

<span class="hljs-keyword">import</span> org.junit.Test;

<span class="hljs-comment">//定义函数式接口</span>
<span class="hljs-meta">@FunctionalInterface</span>
<span class="hljs-class"><span class="hljs-keyword">interface</span> <span class="hljs-title">Printable</span> </span>&#123;
    <span class="hljs-function"><span class="hljs-keyword">void</span> <span class="hljs-title">print</span><span class="hljs-params">(String s)</span></span>;
&#125;

<span class="hljs-comment">//定义含有成员方法类</span>
<span class="hljs-class"><span class="hljs-keyword">class</span> <span class="hljs-title">Method</span> </span>&#123;
    <span class="hljs-function"><span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title">printUpperCaseStr</span><span class="hljs-params">(String s)</span> </span>&#123;
        System.out.println(s.toUpperCase());
    &#125;
&#125;

<span class="hljs-comment">/**
 * <span class="hljs-doctag">@project</span>: jdk-learnig
 * <span class="hljs-doctag">@description</span>: 通过对象名引用成员方法
 * <span class="hljs-doctag">@author</span>: 黄宇辉
 * <span class="hljs-doctag">@date</span>: 8/18/2019-3:07 PM
 * <span class="hljs-doctag">@version</span>: 1.0
 * <span class="hljs-doctag">@website</span>: https://yubuntu0109.github.io/
 */</span>
<span class="hljs-keyword">public</span> <span class="hljs-class"><span class="hljs-keyword">class</span> <span class="hljs-title">RefMethodByObjTest</span> </span>&#123;

    <span class="hljs-function"><span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title">printResult</span><span class="hljs-params">(String s, Printable printable)</span> </span>&#123;
        printable.print(s);
    &#125;

    <span class="hljs-comment">//传统方法</span>
    <span class="hljs-meta">@Test</span>
    <span class="hljs-function"><span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title">testPrintResult</span><span class="hljs-params">()</span> </span>&#123;
        printResult(<span class="hljs-string">"hello lambda"</span>, <span class="hljs-keyword">new</span> Printable() &#123;
            <span class="hljs-meta">@Override</span>
            <span class="hljs-function"><span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title">print</span><span class="hljs-params">(String s)</span> </span>&#123;
                Method obj = <span class="hljs-keyword">new</span> Method(); <span class="hljs-comment">//创建Method对象</span>
                obj.printUpperCaseStr(s); <span class="hljs-comment">//调用对象的成员方法,将字符串转换为大写后输出</span>
            &#125;
        &#125;);
    &#125;

    <span class="hljs-comment">//Lambda表达式写法</span>
    <span class="hljs-meta">@Test</span>
    <span class="hljs-function"><span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title">testPrintResultWithLambda</span><span class="hljs-params">()</span> </span>&#123;
        printResult(<span class="hljs-string">"hello lambda"</span>, s -&gt; &#123;
            Method obj = <span class="hljs-keyword">new</span> Method();
            obj.printUpperCaseStr(s);
        &#125;);
    &#125;

    <span class="hljs-comment">//方法引用写法</span>
    <span class="hljs-meta">@Test</span>
    <span class="hljs-function"><span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title">testPrintResultWithMethodRef</span><span class="hljs-params">()</span> </span>&#123;
        Method obj = <span class="hljs-keyword">new</span> Method();
        printResult(<span class="hljs-string">"hello lambda"</span>, obj::printUpperCaseStr);
    &#125;
&#125;</code></pre></div>

<h4 id="通过类名引用静态方法"><a href="#通过类名引用静态方法" class="headerlink" title="通过类名引用静态方法"></a>通过类名引用静态方法</h4><div class="hljs"><pre><code class="hljs java"><span class="hljs-keyword">package</span> pers.huangyuhui.method;

<span class="hljs-keyword">import</span> org.junit.Test;

<span class="hljs-comment">//定义函数式接口</span>
<span class="hljs-meta">@FunctionalInterface</span>
<span class="hljs-class"><span class="hljs-keyword">interface</span> <span class="hljs-title">calculable</span> </span>&#123;
    <span class="hljs-function"><span class="hljs-keyword">int</span> <span class="hljs-title">add</span><span class="hljs-params">(<span class="hljs-keyword">int</span> x, <span class="hljs-keyword">int</span> y)</span></span>;
&#125;

<span class="hljs-comment">//定义含有静态方法类</span>
<span class="hljs-class"><span class="hljs-keyword">class</span> <span class="hljs-title">Method</span> </span>&#123;
    <span class="hljs-function"><span class="hljs-keyword">public</span> <span class="hljs-keyword">static</span> <span class="hljs-keyword">int</span> <span class="hljs-title">add</span><span class="hljs-params">(<span class="hljs-keyword">int</span> x, <span class="hljs-keyword">int</span> y)</span> </span>&#123;
        <span class="hljs-keyword">return</span> x + y;
    &#125;
&#125;


<span class="hljs-comment">/**
 * <span class="hljs-doctag">@project</span>: jdk-learnig
 * <span class="hljs-doctag">@description</span>: 通过类名引用静态方法
 * <span class="hljs-doctag">@author</span>: 黄宇辉
 * <span class="hljs-doctag">@date</span>: 8/18/2019-3:36 PM
 * <span class="hljs-doctag">@version</span>: 1.0
 * <span class="hljs-doctag">@website</span>: https://yubuntu0109.github.io/
 */</span>
<span class="hljs-keyword">public</span> <span class="hljs-class"><span class="hljs-keyword">class</span> <span class="hljs-title">RefStatisMethodByClazzName</span> </span>&#123;

    <span class="hljs-function"><span class="hljs-keyword">public</span> <span class="hljs-keyword">int</span> <span class="hljs-title">getResult</span><span class="hljs-params">(<span class="hljs-keyword">int</span> x, <span class="hljs-keyword">int</span> y, calculable calculable)</span> </span>&#123;
        <span class="hljs-keyword">return</span> calculable.add(x, y);
    &#125;

    <span class="hljs-comment">//传统写法</span>
    <span class="hljs-meta">@Test</span>
    <span class="hljs-function"><span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title">testGetResult</span><span class="hljs-params">()</span> </span>&#123;
        <span class="hljs-keyword">int</span> result = getResult(<span class="hljs-number">1</span>, <span class="hljs-number">2</span>, <span class="hljs-keyword">new</span> calculable() &#123;
            <span class="hljs-meta">@Override</span>
            <span class="hljs-function"><span class="hljs-keyword">public</span> <span class="hljs-keyword">int</span> <span class="hljs-title">add</span><span class="hljs-params">(<span class="hljs-keyword">int</span> x, <span class="hljs-keyword">int</span> y)</span> </span>&#123;
                <span class="hljs-keyword">return</span> Method.add(x, y);
            &#125;
        &#125;);
        System.out.println(result);
    &#125;

    <span class="hljs-comment">//Lambda表达式写法</span>
    <span class="hljs-meta">@Test</span>
    <span class="hljs-function"><span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title">testGetResultWithLambda</span><span class="hljs-params">()</span> </span>&#123;
        <span class="hljs-keyword">int</span> result = getResult(<span class="hljs-number">1</span>, <span class="hljs-number">2</span>, (x, y) -&gt; Method.add(x, y));
        System.out.println(result);
    &#125;

    <span class="hljs-comment">//方法引用写法</span>
    <span class="hljs-meta">@Test</span>
    <span class="hljs-function"><span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title">testGetResultWithMethodRef</span><span class="hljs-params">()</span> </span>&#123;
        <span class="hljs-keyword">int</span> result = getResult(<span class="hljs-number">1</span>, <span class="hljs-number">2</span>, Method::add);
        System.out.println(result);
    &#125;
&#125;</code></pre></div>

<h4 id="通过Supper引用父类中的成员方法"><a href="#通过Supper引用父类中的成员方法" class="headerlink" title="通过Supper引用父类中的成员方法"></a>通过Supper引用父类中的成员方法</h4><div class="hljs"><pre><code class="hljs java"><span class="hljs-keyword">package</span> pers.huangyuhui.method;

<span class="hljs-keyword">import</span> org.junit.Test;

<span class="hljs-comment">//定义一个函数式接口</span>
<span class="hljs-meta">@FunctionalInterface</span>
<span class="hljs-class"><span class="hljs-keyword">interface</span> <span class="hljs-title">Agreeable</span> </span>&#123;
    <span class="hljs-function"><span class="hljs-keyword">void</span> <span class="hljs-title">greet</span><span class="hljs-params">()</span></span>;
&#125;

<span class="hljs-comment">//定义一个父类</span>
<span class="hljs-class"><span class="hljs-keyword">class</span> <span class="hljs-title">Human</span> </span>&#123;
    <span class="hljs-function"><span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title">hello</span><span class="hljs-params">()</span> </span>&#123;
        System.out.println(<span class="hljs-string">"hello my sun !"</span>);
    &#125;
&#125;

<span class="hljs-comment">/**
 * <span class="hljs-doctag">@project</span>: jdk-learnig
 * <span class="hljs-doctag">@description</span>: 通过Supper引用父类中的成员方法
 * <span class="hljs-doctag">@author</span>: 黄宇辉
 * <span class="hljs-doctag">@date</span>: 8/18/2019-4:06 PM
 * <span class="hljs-doctag">@version</span>: 1.0
 * <span class="hljs-doctag">@website</span>: https://yubuntu0109.github.io/
 */</span>
<span class="hljs-keyword">public</span> <span class="hljs-class"><span class="hljs-keyword">class</span> <span class="hljs-title">RefMethodBySupper</span> <span class="hljs-keyword">extends</span> <span class="hljs-title">Human</span> </span>&#123;

    <span class="hljs-meta">@Override</span>
    <span class="hljs-function"><span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title">hello</span><span class="hljs-params">()</span> </span>&#123;
        System.out.println(<span class="hljs-string">"hello my father !"</span>);
    &#125;

    <span class="hljs-function"><span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title">printResult</span><span class="hljs-params">(Agreeable agreeable)</span> </span>&#123;
        agreeable.greet();
    &#125;

    <span class="hljs-comment">//传统写法</span>
    <span class="hljs-meta">@Test</span>
    <span class="hljs-function"><span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title">testPrintResult</span><span class="hljs-params">()</span> </span>&#123;
        printResult(<span class="hljs-keyword">new</span> Agreeable() &#123;
            <span class="hljs-meta">@Override</span>
            <span class="hljs-function"><span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title">greet</span><span class="hljs-params">()</span> </span>&#123;
                RefMethodBySupper.<span class="hljs-keyword">super</span>.hello();
            &#125;
        &#125;);
    &#125;

    <span class="hljs-comment">//Lambda表达式写法</span>
    <span class="hljs-meta">@Test</span>
    <span class="hljs-function"><span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title">testPrintResultWithLambda</span><span class="hljs-params">()</span> </span>&#123;
        printResult(() -&gt; <span class="hljs-keyword">super</span>.hello());
    &#125;

    <span class="hljs-comment">//方法引用写法</span>
    <span class="hljs-meta">@Test</span>
    <span class="hljs-function"><span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title">testPrintResultWithMethodRef</span><span class="hljs-params">()</span> </span>&#123;
        printResult(<span class="hljs-keyword">super</span>::hello);
    &#125;

&#125;</code></pre></div>

<h4 id="通过this引用成员方法"><a href="#通过this引用成员方法" class="headerlink" title="通过this引用成员方法"></a>通过this引用成员方法</h4><div class="hljs"><pre><code class="hljs java"><span class="hljs-keyword">package</span> pers.huangyuhui.method;

<span class="hljs-keyword">import</span> org.junit.Test;

<span class="hljs-comment">//定义函数式接口</span>
<span class="hljs-meta">@FunctionalInterface</span>
<span class="hljs-class"><span class="hljs-keyword">interface</span> <span class="hljs-title">Supermarket</span> </span>&#123;
    <span class="hljs-function"><span class="hljs-keyword">void</span> <span class="hljs-title">buy</span><span class="hljs-params">()</span></span>;
&#125;

<span class="hljs-comment">/**
 * <span class="hljs-doctag">@project</span>: jdk-learnig
 * <span class="hljs-doctag">@description</span>: 通过this引用成员方法
 * <span class="hljs-doctag">@author</span>: 黄宇辉
 * <span class="hljs-doctag">@date</span>: 8/18/2019-4:30 PM
 * <span class="hljs-doctag">@version</span>: 1.0
 * <span class="hljs-doctag">@website</span>: https://yubuntu0109.github.io/
 */</span>
<span class="hljs-keyword">public</span> <span class="hljs-class"><span class="hljs-keyword">class</span> <span class="hljs-title">RefMethodByThis</span> </span>&#123;

    <span class="hljs-function"><span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title">buyLaptop</span><span class="hljs-params">()</span> </span>&#123;
        System.out.println(<span class="hljs-string">"buy a laptop successfully"</span>);
    &#125;

    <span class="hljs-function"><span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title">printResult</span><span class="hljs-params">(Supermarket supermarket)</span> </span>&#123;
        supermarket.buy();
    &#125;

    <span class="hljs-comment">//传统写法</span>
    <span class="hljs-meta">@Test</span>
    <span class="hljs-function"><span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title">testPrintResult</span><span class="hljs-params">()</span> </span>&#123;
        printResult(<span class="hljs-keyword">new</span> Supermarket() &#123;
            <span class="hljs-meta">@Override</span>
            <span class="hljs-function"><span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title">buy</span><span class="hljs-params">()</span> </span>&#123;
                buyLaptop();
            &#125;
        &#125;);
    &#125;

    <span class="hljs-comment">//Lambda表达式写法</span>
    <span class="hljs-meta">@Test</span>
    <span class="hljs-function"><span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title">testPrintResultWithLambda</span><span class="hljs-params">()</span> </span>&#123;
        printResult(() -&gt; <span class="hljs-keyword">this</span>.buyLaptop());
    &#125;

    <span class="hljs-comment">//方法引用写法</span>
    <span class="hljs-meta">@Test</span>
    <span class="hljs-function"><span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title">testPrintResultWithMethodRef</span><span class="hljs-params">()</span> </span>&#123;
        printResult(<span class="hljs-keyword">this</span>::buyLaptop);
    &#125;

&#125;</code></pre></div>

<h4 id="类的构造器引用"><a href="#类的构造器引用" class="headerlink" title="类的构造器引用"></a>类的构造器引用</h4><div class="hljs"><pre><code class="hljs java"><span class="hljs-keyword">package</span> pers.huangyuhui.method;

<span class="hljs-keyword">import</span> org.junit.Test;

<span class="hljs-comment">//定义函数式接口</span>
<span class="hljs-meta">@FunctionalInterface</span>
<span class="hljs-class"><span class="hljs-keyword">interface</span> <span class="hljs-title">UserBuilder</span> </span>&#123;
    <span class="hljs-function">User <span class="hljs-title">builder</span><span class="hljs-params">(String name)</span></span>;
&#125;

<span class="hljs-comment">//定义含待引用的构造方法类</span>
<span class="hljs-class"><span class="hljs-keyword">class</span> <span class="hljs-title">User</span> </span>&#123;
    <span class="hljs-keyword">private</span> String name;

    <span class="hljs-function"><span class="hljs-keyword">public</span> <span class="hljs-title">User</span><span class="hljs-params">(String name)</span> </span>&#123;
        <span class="hljs-keyword">this</span>.name = name;
    &#125;

    <span class="hljs-function"><span class="hljs-keyword">public</span> String <span class="hljs-title">getName</span><span class="hljs-params">()</span> </span>&#123;
        <span class="hljs-keyword">return</span> name;
    &#125;

    <span class="hljs-function"><span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title">setName</span><span class="hljs-params">(String name)</span> </span>&#123;
        <span class="hljs-keyword">this</span>.name = name;
    &#125;

&#125;

<span class="hljs-comment">/**
 * <span class="hljs-doctag">@project</span>: jdk-learnig
 * <span class="hljs-doctag">@description</span>: 类的构造器引用
 * <span class="hljs-doctag">@author</span>: 黄宇辉
 * <span class="hljs-doctag">@date</span>: 8/18/2019-7:09 PM
 * <span class="hljs-doctag">@version</span>: 1.0
 * <span class="hljs-doctag">@website</span>: https://yubuntu0109.github.io/
 */</span>
<span class="hljs-keyword">public</span> <span class="hljs-class"><span class="hljs-keyword">class</span> <span class="hljs-title">RefConstructor</span> </span>&#123;

    <span class="hljs-function"><span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title">printResult</span><span class="hljs-params">(String name, UserBuilder userBuilder)</span> </span>&#123;
        User user = userBuilder.builder(name);
        System.out.println(user.getName());
    &#125;

    <span class="hljs-comment">//传统写法</span>
    <span class="hljs-meta">@Test</span>
    <span class="hljs-function"><span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title">testPrintResult</span><span class="hljs-params">()</span> </span>&#123;
        printResult(<span class="hljs-string">"yubuntu0109"</span>, <span class="hljs-keyword">new</span> UserBuilder() &#123;
            <span class="hljs-meta">@Override</span>
            <span class="hljs-function"><span class="hljs-keyword">public</span> User <span class="hljs-title">builder</span><span class="hljs-params">(String name)</span> </span>&#123;
                <span class="hljs-keyword">return</span> <span class="hljs-keyword">new</span> User(name);
            &#125;
        &#125;);
    &#125;

    <span class="hljs-comment">//Lambda表达式写法</span>
    <span class="hljs-meta">@Test</span>
    <span class="hljs-function"><span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title">testPrintResultWithLambda</span><span class="hljs-params">()</span> </span>&#123;
        printResult(<span class="hljs-string">"yubuntu0109"</span>, s -&gt; <span class="hljs-keyword">new</span> User(s));
    &#125;

    <span class="hljs-comment">//方法引用写法</span>
    <span class="hljs-meta">@Test</span>
    <span class="hljs-function"><span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title">testPrintResultWithMethodRef</span><span class="hljs-params">()</span> </span>&#123;
        printResult(<span class="hljs-string">"yubuntu0109"</span>, User::<span class="hljs-keyword">new</span>);
    &#125;

&#125;</code></pre></div>

<h4 id="数组的构造器引用"><a href="#数组的构造器引用" class="headerlink" title="数组的构造器引用"></a>数组的构造器引用</h4><div class="hljs"><pre><code class="hljs java"><span class="hljs-keyword">package</span> pers.huangyuhui.method;

<span class="hljs-keyword">import</span> org.junit.Test;

<span class="hljs-keyword">import</span> java.util.Arrays;

<span class="hljs-comment">//定义函数式接口</span>
<span class="hljs-meta">@FunctionalInterface</span>
<span class="hljs-class"><span class="hljs-keyword">interface</span> <span class="hljs-title">ArrayBuilder</span> </span>&#123;
    <span class="hljs-keyword">int</span>[] builderArray(<span class="hljs-keyword">int</span> length);
&#125;

<span class="hljs-comment">/**
 * <span class="hljs-doctag">@project</span>: jdk-learnig
 * <span class="hljs-doctag">@description</span>: 数组的构造器引用
 * <span class="hljs-doctag">@author</span>: 黄宇辉
 * <span class="hljs-doctag">@date</span>: 8/18/2019-7:51 PM
 * <span class="hljs-doctag">@version</span>: 1.0
 * <span class="hljs-doctag">@website</span>: https://yubuntu0109.github.io/
 */</span>
<span class="hljs-keyword">public</span> <span class="hljs-class"><span class="hljs-keyword">class</span> <span class="hljs-title">RefArrayConstructor</span> </span>&#123;

    <span class="hljs-keyword">public</span> <span class="hljs-keyword">static</span> <span class="hljs-keyword">int</span>[] getArray(<span class="hljs-keyword">int</span> length, ArrayBuilder arrayBuilder) &#123;
        <span class="hljs-keyword">return</span> arrayBuilder.builderArray(length);
    &#125;

    <span class="hljs-comment">//传统写法</span>
    <span class="hljs-meta">@Test</span>
    <span class="hljs-function"><span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title">testgetArray</span><span class="hljs-params">()</span> </span>&#123;
        <span class="hljs-keyword">int</span>[] array = getArray(<span class="hljs-number">10</span>, <span class="hljs-keyword">new</span> ArrayBuilder() &#123;
            <span class="hljs-meta">@Override</span>
            <span class="hljs-keyword">public</span> <span class="hljs-keyword">int</span>[] builderArray(<span class="hljs-keyword">int</span> length) &#123;
                <span class="hljs-keyword">return</span> <span class="hljs-keyword">new</span> <span class="hljs-keyword">int</span>[length];
            &#125;
        &#125;);
        System.out.println(Arrays.toString(array));
    &#125;

    <span class="hljs-comment">//Lambda表达式写法</span>
    <span class="hljs-meta">@Test</span>
    <span class="hljs-function"><span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title">testArrayWithLambda</span><span class="hljs-params">()</span> </span>&#123;
        <span class="hljs-keyword">int</span>[] array = getArray(<span class="hljs-number">10</span>, length -&gt; <span class="hljs-keyword">new</span> <span class="hljs-keyword">int</span>[length]);
        System.out.println(Arrays.toString(array));
    &#125;

    <span class="hljs-comment">//方法引用写法</span>
    <span class="hljs-meta">@Test</span>
    <span class="hljs-function"><span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title">testArrayWithMethodRef</span><span class="hljs-params">()</span> </span>&#123;
        <span class="hljs-keyword">int</span>[] array = getArray(<span class="hljs-number">10</span>, <span class="hljs-keyword">int</span>[]::<span class="hljs-keyword">new</span>);
        System.out.println(Arrays.toString(array));
    &#125;
&#125;</code></pre></div>
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